Telecommunications base stations transmit and receive signals to and from remote communication devices, such as cellular telephones or radios. In order for the base station to transmit a signal, base-band data is up-converted and amplified by a power amplifier. RF output of the power amplifier is then filtered, and sent to a transmit antenna. Typically, the path between the transmit filter and the antenna includes various connectors and cables (e.g., 50 Ω RF antenna cable).
If the cables, connectors or other components of the transmit path are misconnected, damaged or otherwise faulty, it is likely that a mild to severe impedance mismatch will exist for the transmitted signal. This can result in a degraded or interrupted signal. Accordingly, when these mismatches are present, it is important to accurately determine the location and source of the problem.
In order to locate an impedance mismatch using prior art methods, a human operator is required to disconnect cables and connectors along the transmit path, and insert external test equipment to approximate the mismatch location. For example, an operator can manually insert a Time-Domain Reflectometer (TDR) along the transmit path. The TDR then sends out a signal along the transmit path, and measures the magnitude of any signal that is reflected back to the TDR. These measurements give an indication of the location of the impedance mismatch so that the problem can be corrected.
Because insertion of external equipment requires the operator to disconnect portions of the transmit path, one disadvantage to prior art systems is that it is necessary to interrupt normal transmissions in order to diagnose a problem. In addition, the external test equipment generally is expensive, and requires an operator to be trained and proficient at using the equipment.
There is a need to accurately estimate the locations of impedance mismatches along the transmit path of an RF communication system without interrupting normal transmissions. There is a further need to locate such impedance mismatches without the use of external test equipment